Metal paper fasteners for holding stacks of perforated paper have been devised which are constructed in two basic parts, namely a rectangular base member terminating in a narrow tongue portion at each end and a rectangular compressor which is provided with a transverse tongue-receiving slot adjacent each end thereof. One such fastener has a compressor in which each tongue of the base member is passed through the respective slot in the compressor and then a sharp edge of the tongue has to be pushed into a slit provided in a longitudinal ridge which is provided and extends along the top ede of the compressor. Such a ridge may also have opposed hooks. However, in order close or open the fastener it is usually necessary for the user to apply finger force to the sharp and mostly buried locked under edge of the tongue which can result in cut fingers. Other similar fasteners have locking lugs in the tongues and even ramped members in the compressor and a common feature to all is that when the tongue is pushed flat against the compressor it is usually necessary to bend or twist the tongue off-centre to the longitudinal axis of the compressor. Considerable force is then required to release the locked tongue and cut fingers can result because of the sharp edges and is frequently also necessary to use a tool or instrument to prise out the locked tongue. In another design the edges of the transverse slots of the compressor are turned out to form lips which grip the tongue when the tongue is passed down through the slots and under the compressor for locking purposes. However such locking edges would make the tongue difficult to disengage from the compressor. In yet another design a binder has back and front covers used in conjunction with a cord which can be secured in channel slots in the compressor and separate nylon locking elements are then mounted on the compressor but labor production costs would make the production of the separate components of different materials a costly and uneconomical proposition and clamping and releasing actions would not be satisfactory. Such metal component paper fasteners are prone to rust and the tongues will break off because of metal fatigue.
It is an object of this invention to provide a paper fastener which has quicker and easier locking and release actions.
Another object is to provide a paper fastener which is of economical construction, light in weight and which is rustproof and durable.
Another object is to provide a paper fastener all the components of which have smooth non-cutting edges and which is therefore safer to use.
Another object is to provide an improved two-piece paper fastener in which resilient hooks on the compressor enable a snap-fit locking action with the tongues and in which co-operating complementary members on the compressor and tongues prevent accidental transverse and longitudinal slipping of the tongues from the compressor but enable quick and easy release during unfastening.